5_functions.js

//* ===============================
//* Function in JavaScript
//* ==============================
//? In JavaScript, a function is a block of reusable code that performs a specific task or set of tasks. Functions are used to organize code into modular and manageable pieces, promote code reuse, and make programs more readable.

//  3 students at a same time wants to find the sum of two numbers

// 1st student
// var a = 5,
//   b = 10;
// var sum1 = a + b;
// console.log(sum1);

// // 2nd student
// var a = 15,
//   b = 15;
// var sum2 = a + b;
// console.log(sum2);

// // 3rd student
// var a = 55,
//   b = 15;
// var sum3 = a + b;
// console.log(sum3);

// lets make a reusable code

// function sum(a, b) {
//   return a + b;
// }

// console.log(sum(5, 5));
// console.log(sum(15, 50));
// console.log(sum(25, 750));

//* ===============================
//* Function Declaration:
//* ==============================

//? Declare a function using the function keyword, followed by the function name, parameters (if any), and the function body.
//? This step defines the function and specifies what code should be executed when the function is called.

// function greet() {
//   console.log("Hello Guys, Welcome to Thapa Technical JS Course ");
// }

//* =================================================
//* Function Invocation (Calling a Function):
//* =================================================

//?After declaring a function, you can invoke or call it by using its name followed by parentheses.
//? If the function has parameters, provide values (arguments) for those parameters inside the parentheses.

//? How to call a function
// greet();

//! Practice Time
//! 1. Write a function to find the sum of two numbers.

//todo Tips "1st declare the function & then call it" In JavaScript, it's a good practice to declare (define) your functions before you call them. This ensures that the function is available for use when you try to call it.

// Function definition

// function sum(){
//     var a=5, b=10;
//     console.log(a+b);
// }
// sum();
// Calling the function

//* ==============================
//* Function Parameter:
//* ==============================

//? A function parameter is a variable that is listed as a part of a function declaration. It acts as a placeholder for a value that will be provided when the function is called. Parameters allow you to pass information into a function, making it more versatile and reusable.

// Syntax: function functionName(parameter1, parameter2, ...params) {
//   // Function body
//   // Code to be executed when the function is called
// }

//* ==============================
//* Function Argument:
//* ==============================

//? A function argument is a value that you provide when you call a function. Arguments are passed into a function to fill the parameters defined in the function declaration.

//? syntax:
//? functionName(argument1, argument2, ...);

//! Practice Time
//? Let's say we want to greet students with one same line
//! Write a JavaScript program that defines a function called greet to welcome individuals to the JS Course. The function should take a name parameter and output the message "Hello [name], Welcome to JS Course". Call the function twice, once with the argument "vinod" and once with the argument "ram".

// function greet(name){
//     console.log("Hello " + name + ", Welcome to JS Course");
// }

// greet("Vanshika");

//! 1. Write a function to find the sum of two numbers with parameters.
// function sum(a,b){
//     console.log(a+b);
// }
// sum(5,19);

//* ==============================
//* Function expressions
//* ==============================
//? A function expression is a way to define a function as part of an expression. It can be either named or anonymous. If it's named, it becomes a named function expression.

// var result = function sum(a,b){
//        console.log(a+b);
//         };

// result(10,15);

//* ==============================
//*  Anonymous Function
//* =============================
//? An anonymous function is a function without a name. It can be created using either a function expression or a function declaration without a specified name.

// var result = function (a,b){
//        console.log(a+b);
//         };

// result(10,15);

//* ==============================
//*  Return Keyword
//* =============================
//? Return Keyword: In JavaScript, the return statement is used within a function to specify the value that the function should produce or provide back to the code that called it. The return statement stops the execution of a function and sends a value back to the caller

//? Syntax
// return expression;

//! Example 1: Returning a Sum of two number
// function sum(a, b) {
//   return a + b;
// }

// var result = sum(5,5);
// console.log(result);


//* ==============================
//* IIFE - immediately invoked function expression
//* =============================
//? An IIFE, or Immediately Invoked Function Expression, is a JavaScript function that is defined and executed immediately after its creation. It is a way to create a self-contained block of code that doesn't interfere with the surrounding code and executes immediately

// Syntax
// (function () {
//   // code to be executed
// })();

// var result = (function (a,b){
//     console.log(a+b);
// })(5,10);

// !Practice Time ( IIFE with Parameters)

//? Interview Questions

//! Question 1: Calculator Function
//! Write a JavaScript function calculator that takes two numbers and an operator as parameters and returns the result of the operation. The function should support addition, subtraction, multiplication, and division.

// const calculator = (num1, num2, operator) => {
//   let result;
//   switch (operator) {
//     case "+":
//       return num1 + num2;

//     case "-":
//       result = num1 - num2;
//       return result;

//     case "*":
//       result = num1 * num2;
//       return result;

//     case "/":
//       if (num2 === 0) {
//         return "0 is not allowed";
//       } else {
//         result = num1 / num2;
//         return result;
//       }

//     default:
//       return "no operator found";
//   }
// };
// console.log(calculator(5,2,"+"));
// console.log(calculator(5,2,"-"));
// console.log(calculator(5,0,"/"));

//! Reverse a String:
//! Write a function to reverse a given string without using built-in reverse methods.

// const isReverse = (str) => {
//     let reverse = "";
//     for (let char = str.length - 1; char >= 0; char--) {
//       reverse = reverse + str[char];
//     }
//     return reverse;
//   };
  
//   console.log(isReverse("vanshika thesiya"));

  
//! Palindrome Check:
//! Create a function to determine if a given string is a palindrome (reads the same backward as forward).

// const isPalindrome = (str) => {
//     let reverse = "";
//     for (let char = str.length - 1; char >= 0; char--) {
//       reverse = reverse + str[char];
//     }
//     //   if (str === reverse) {
//     //     return true;
//     //   } else {
//     //     return false;
//     //   }
  
//     return str === reverse ? true : false;
//   };
  
//   console.log(isPalindrome("level"));